Multiple gravity and float concentrator



July 15, 1958 N. L MATTHEWS MULTIPLE GRAVITY, AND FLOAT CONCENTRATOR Filed April 10, 1957 2 Sheets-Sheet 1 ATTORNEYS y 5, 1958 N. 1.. MATTHEWS 2,843,266

MULTIPLE GRAVITY AND FLOAT CONCENTRATOR Filed April 10, 1957 2 Sheets-Sheet 2 v 4 T '1: E

INVENTOR NEWTON L. MAT-71mm BY Y ATTQRNEYS United States Patent MULTIPLE GRAVITY AND FLOAT CONCENTRATOR This invention relates primarily to the treatment of minerals and more particularly to an apparatus for separating and grading granularmaterial, such as ore, in

accordance with the specific gravity of the materials to be separated.

Various types of gravity and float concentrating apparatus have been heretofore proposed and utilized, but the majority of these concentrators were designed to be utilized with a particular type of mineral or material having a given specific gravity and Where it was desired to separate and concentrate minerals or materials of other specific gravities, it was necessary to provideseparate concentrating apparatus therefor. Furthermore, such concentrators are subject to considerable wear due -to the abrasive action of the materials flowing therethrough and in the majority of previously used concentrators of this type, it was necessary to replace the samewhen Wear became excessive, thus materially increasing the cost of treating ore to separate and concentrate the minerals contained therein. It was also necessary with these priorart concentrators to utilize a relatively large volumeof water, thus necessitating the location of concentrating plants where Water was plentiful.

It is accordingly an object of the invention to provide a multiple gravity and float concentrator for automatically separating minerals of different specific gravities from material fed thereto, together With means for discharging the separate minerals from the apparatus.

A further object of the invention is the provision of a multiple gravity and float concentrator, including a rotating drum and in which separating riflles provided on the strips of yieldable removable materialare disposed on the inner surface of the drum to permit separation of materials according to their. specific gravities.

A still further object of the invention is theprovision ofa multiple gravity and float concentrator inwhich a rotatable drum is provided with a removable yieldable lining which may be conveniently replaced in. theevent of excessive wear thereby precluding replacement of the entire drum.

Another object of the invention is the provisionof a multiple gravity and float concentrator includinga rotatable drum and in which strips of yieldable material having riflies formed thereon are removably disposed in the drum thereby permitting the use of rifl'les of' different depths to separate materials of different specific gravities without necessitating providing separate apparatus therefor.

Another object of the invention is the provision of a multiple gravity and float concentrator including a rotatable drum having spaced riflies of varying depth on the inner surface thereof and in which the spaces .between the rifiies are automatically cleaned .upon. each revolution of the drum.

A further object of the invention is the provision of a multiple gravity and float concentrator including: a, rotatable drum and in which the entire inner. surfaceof 2,843,266 Patented July 15, 1958 2 the-drum is covered with a yieldable material whichis highly resistant to abrasive action and in which spaced rifiles are formed as an integral part of suchtlining material.

Further objects and advantages of the invention will be apparent'from the following description taken in conjunction with the accompanying drawing wherein:

Fig. 1 is a longitudinal sectional view taken substantially-on the line 1-1 of Fig. 2 and showing the internal structure of the rotating drum forming the main operating element of the apparatus of this invention;

Fig. 2 an end elevational view with parts in section for greater clarity and showing the mounting for the rotating drum, as wellas the structure of the lower end thereof and the mounting means for the delivery troughs receiving separated materials from said drum;

Fig. 3 a sectional view taken substantially on the line 3-3 of Fig. 4 and showing the structure. of a riffle, mat and the fin carried thereby;

Fig. 4 a sectional view taken substantially on theline 4- 4 of-Fig. 3 and showing the configuration of the, recess in the fin; and a Fig. 5 a sectional view taken substantially on the line 5-5 of Fig. 1 and showing a riffle mat in placev in the drum.

With continued reference to the drawing, there is shown an apparatus constructed in accordance with this invention and which may well comprise a frame ,constructed of suitable structural shapes, such as angle iron or the like and including longitudinal base members 10, corner posts 11 at one end thereof and corner posts 12 at the opposite end. Cross members 13 may alsobe provided at each end'of the frame and if desired, the corner posts-11 and 12 may be secured to the base members 16 by gusset plates 14. Itwill benoted, that thecorner posts 11 are considerably higher. thanthecorner posts 12 and the reason for'this difference in height will presently appear.

Extending between the corner posts 11 and 12-at each side of the frame are longitudinal frame members 15 and mounted on such frame members'15 are bearings 16 which serve to rotatably support substantiallywparallel shafts 17 and 18. Fixed to shaft.18 are spaced rollers 19 and similar spaced rollers 20 are carried, by the shaft 17. The shaft 18 maybe provided With-a suitable sprocket or pulley 21 for engaging a. flexible drive member in order to drive and rotate the shaft 18 and rollers 19 carried thereby for a purposewhich: will presently appear.

It is further to. be noted, that the longitudinal frame members 15 and the shafts 17 .and18 carried thereby are inclined from the horizontal and mounted. on the rollers 19 and 20 and supported thereby is a drum,22 open at both ends. The drum,22 may be formed .of metal or other suitable material and since the sameis supported on the rollers. 19 and 20, the. drum 22. will rotate upon rotation of the shaft 18 by means of a belt or chain engaging the sprocket or pulley 21.

An annular baffle 23 is secured to the. inner surface of the drum 22 at the lower end thereof and the bafile 23 serves to provide a central discharge iopeningld. As best shown in Fig.2, the annular baffle. 23. is. provided with a plurality of angularly spaced segmental apertures 25 adjacent the inner surface of the, drum 22 and while six such apertures have been shown in .the drawing, obviously, any desired number may be provided. An annular valve plate 26, is disposed in the drum 22 in engagement with the inner surface of the baffle 23 and the valve plate 26 is provided with a plurality of angularly spaced segmental apertures 27 in alignment with the. apertures 25 in the baffle 23. The

the plate 26 and the bolt 29 may extend through each slot 28 and an aperture in the baffle 23, there being a wing nut 30 engaging the outer end of each bolt 29 to securely clamp the valve plate 26 in adjusted position.

A yieldable lining, such as a strip of rubber or other suitable material 31 may be applied to the inner side of the drum 22 adjacent the inner surface of the valve plate 26 and the lining 31 may be secured in place by any suitable means. A rifile mat 32 is positioned in the drum 22 with the lower end thereof overlapping the upper edge of the lining 31 and a second riflle mat 33 is disposed in the drum 22 in engagement with the inner surface thereof and with the lower edge overlapping the upper edge of the riffle mat 32. A third riflle mat 34 is also positioned in" the drum 22 in engagement with the inner surface thereof and with the lower edge overlapping the upper edge of the riflle mat 33. The remainder of the inner surface of the drum 22 at the upper end, is covered by a lining 35 of yieldable material, such as rubber or the like.

As best shown in Figs. 1, 3 and 4, the riflle mat 32 may well comprise a strip of yieldable material, such as rubber or the like, such strip being provided with inwardly extending ribs .35 of the desired depth. The mat 32 is likewise provided with an integral longitudinal inwardly extending fin 36 having an arcuate elongated longitudinal recess 37 in one side thereof, the recess 37 being closed at opposite ends 38 and 39 as shown in Fig. 3. As best shown in Fig. 4, the strip forming the riflle mat 32 may be provided with a tongue 40 which may be received in a groove 41 in the opposite end thereof when the mat is installed within the drum 22 in engagement with the :inner surface thereof and with the ribs or rifl'les 35' extending around the inner surface of the drum 22. It is also to be noted, that the mat 32 is provided at one end with an offset recess 42 for extending over the upper edge of the lining 31 in the drum 22. The riflle mat 32 'may be conveniently installed in the drum 22 merely by folding the same for insertion and thereafter allowing the same to expand into contact with the inner surface of the drum 22, at which time the tongue 40 may be introduced into the groove 41 thereby locking the mat 32 in place in the drum 22. Obviously, the mat 32 may be replaced upon undue Wear thereof or for the purpose of providing riffles 35' of a different depth.

Riflle mats 33 and 34 are formed in substantially the same manner as mat 32 described above, and consequently a further detailed description of mats 33 and 34 is not considered necessary or desirable, since the same would be merely repetition of the description given above in connection with mat 32. It is to be noted, however, that the second riflie mat 33 is provided with ribs or riffies 43 of less depth than the riflles 35' and also that the mat 34 is provided with riflles 44 of less depth than the rifiles 43,0n the second mat 33. As a consequence, the riflles 35', 43 and 44 decrease in depth from the lower end of the drum 22 toward the upper end thereof. It is furtherto be noted, that each rifile mat and the lining 35' overlap the 'upper edge of the next lower riflle mat and as a consequence, water and granular material to be treated may flow downwardly along the inner surface of the linings and mats without contacting the inner surface of the drum 22. Also the. second riffle mat 33 is provided with a fin 45 similar to the fin 36 on the mat 32, and another similar fin 46 is provided on the riflle mat 34. 1 An inwardly extending annular flange 47 is secured in the upper end of the drum 22 and such flange 47 serves to provide a central inlet opening 48. A spout 49 projects through the inlet opening 48 in the flange 47 and the lower end 50 of the spout 49 is disposed below the normal level of water in the drum 22, such level being indicated by the dotted line 51. The spout 49 may be provided with a hopper 52 or other means for introducing granular material, such as ore, thereto and also there may be provided a water supply in the form of a pipe 53 projecting into the hopper 52 and provided with a valve or other suitable means 54 for controlling the flow of Water into the hopper 52 and spout 49.

An inclined frame member 55 projects from the upper end of the corner posts 11 through the inlet opening 48 in the flange 47 and through the drum 22 with the lower end of the frame member 55 extending through the discharge opening 24 in the baflle 23 and being secured to the upper ends of corner posts 12. Inclined frame member 55 serves to support a plurality of troughs or launders 56, 57 and 58. It should be noted, that the trough 58 terminates at the inner end at a point above the upper riflle in the first riflle mat 32, while the trough 57 extends inwardly to a point above the upper riflle 43 on the riflle mat 33. The trough 56 projects to a point above the upper rifile 44 on the riflle mat 34 and the outer ends of the troughs 56, 57 and 58 extend outwardly of the drum 22 through the discharge opening 24.

In operation, ore or other granular material to be treated is deposited in the hopper 52 of the spout 49 and is mixed with water from the pipe 53 to form a slurry which moves downwardly and is discharged through the lower end 50 of the spout 49 into the drum 22 between the upper riflle 44 of the mat 34 and the annular flange 47 at the upper end of the drum 22. The drum 22 is slowly rotated and the same is filled with water to the level indicated by the line 51. This level is maintained by proper adjustment of the valve plate 26 to control the discharge of water through the openings provided by the apertures 25 and 27 in the baflle 23 and valve plate 26. As the water and granular material flows downwardly in the drum 22, the particles of greatest weight will lodge behind the riffles 44 of the upper riffle mat 34 while particles of progressively less weight will lodge behind the riflies 43 of mat 33 and riifles 35 of mat 32. Rotation of the drum 22 will result in the material lodged behind the riflles being carried upwardly by the fin 36 and since water will also be carried thereby due to the recess 37 therein, such water and granular material will be deposited in the troughs 56, 57 and 58 when the fins 36, 45 and 46 reach their uppermost position over such troughs. In view of the disposition of the troughs 56, 57 and 58, the material collected by the riffles 44 of mat 34 will be deposited in the trough 56 while the material collected by the riflles 43 of mat 33 will be deposited in the trough 57. In a similar manner, the materials collected behind the riflies 35' of the mat 32 will be deposited in the trough 58. As a result, materials having three different specific gravities will be separated by the apparatus of this invention and deposited in individual troughs to 'be discharged from the apparatus and collected in any desired manner. It is also to be noted, that any material floating on the surface of the water in the drum 22 will be discharged therefrom, together with the water flowing through the discharge opening 24 in the baffie 23. The flow through the apertures 25 and 27 provided 'by the baflle 23 and valve plate 26 will be waste water and waste rock materials since all desired materials heavier than rock will have been collected behind the riffles on one of the riflle mats 32, 33 or 34 and deposited in the appropriate troughs 56, 57 or 58.

- As stated above,the depth of the riflles utilized is determined by the specific gravity of the particular materials being concentrated or collected and consequently, the apparatus of this invention provides a convenient means for varying the depth of such riflles, since it is only necessary to remove the mats carrying the riflles and install other mats having riflies of different depth. Also, since the mats are subjected to considerable abrasion, replacement thereof after undue wear is facilitated by the particular design which merely permits placing the flexible and yieldable mats within the drum, such mats being held therein by the resilience of the material. While the inclination of the drum 22 is shown in the drawing as being fixed, nevertheless, suitable mechanism may be provided to vary the inclination thereof in accordance with the particular material 'being treated and furthermore, it is to be understood, that suitable means will be provided for varying the speed of rotation of the drum 22 in order to provide the necessary time for collection of particles behind the riffles on the inner surface thereof.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited bythat which is shown in the drawing and described in the specification, but only as indicated in the appended claims.

What is claimed is:

l. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baflie secured to the inner surface of said drum at the lower end, a central discharge opening in'said baffle, a plurality of angularly spaced segmental apertures in said baffle adjacent the inner surface of said drum, an annular valve plate engaging the inner radial surface of said baflie, a plurality of angularly spaced segmental apertures in said plate in alignment with the apertures in said baffle, said plate being rotatable with respect to said baffle to vary the area of the openings provided by said apertures, means to fix said plate in adjusted position, a yieldable lining on the inner surface of said drum adjacent said plate, a rifiie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said mat overlapping the upper edge of said lining, spaced inwardly extending annular ribs on said mat providing riflies, a longitudinally inwardly extending fin on said mat, anelongated arcuate longitudinal recess in one side of saidfin, said recess being closed at opposite ends, a second ritfle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said second mat overlapping the upper edge of said first mat, spaced rifiies on said second mat of less depth than said first mentioned riffles, a longitudinal inwardly extending fin on said second mat and having an elongated arcuate longitudinal recess in one side closed at opposite ends, a third riflle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of saidthird mat overlapping the'upper edge of said second mat, spaced riifles on said third mat of less depth than said second mentioned riffles, a longitudinal inwardly extending fin on said third mat and having an elongated arcuate longitudinal recess in one side closed at opposite ends, an inwardly extending annular flange at the upper end of said-drum providing a central inlet opening, ayieldable lining on the inner surface of said drum between said flange and said third mat and overlapping the upper edge of said third mat, means for feed ing water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said rifiles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving mate rial from each fin.

2; An apparatus asdefined in claim 1, in which said 6 means for feeding water and granular material through said inlet opening into said drum comprises a-spout terminating within said drum between said flange and the upper edge of said third mat and below the normal level of water within said drum.

3. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baffle, a plurality of angularly spaced apertures in said batlie, an annular valve plate engaging the inner radial surface of said baffle, a plurality of angularly spaced apertures in said plate in alignment with the apertures in said baffle, said plate being rotatable with respect to said bafile to vary the area of the openings provided by said apertures, means to fix said plate in adjusted position, a yieldable lining on the inner surface of said drum adjacent said plate, a riflie mat comprising a strip of yieldable material removably disposed in said .drum in engagement with the inner surface, the lower edge of said mat overlapping the upper edge of said lining, spaced inwardly extending annular ribs on said mat providing riffles, a longitudinal inwardly extending fin on said mat, an elongated arcuate longitudinal recessvin one side of said fin, said recess'being closed at opposite ends, a second riffle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said second mat overlapping theupper edge of said firstmat, spaced riffles on said second mat of less depth than said first mentioned riifles, a longitudinal inwardly extending fin on said second mat and having an elongated arcuate longitudinal recess in one side closed at opposite ends, a third riffie mat comprising a strip of yieldable material removably disposed in .said drum in engagement with the inner surface, the lower edge of .said third mat overlapping the upper edge of said second mat, spaced riflles on said third mat of less depth than said second mentioned rifiles, a longitudinal inwardly extending fin on said third mat and having an elongated arcuate longitudinal recess in one side closed at opposite ends, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, a yieldable lining on the inner surface of said drum between said flange and said third mat and overlappingthe upper edge of said third mat, means for feeding water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum waternand granular material retained by said riflies will betcarried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

4. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drumbeing open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said .drum at the lower end, a central discharge opening at said bafile, a plurality of angularly spaced apertures. in said baffle, an annular valve plate engaging the inner radial surface of said baffle, a plurality of angularly, spaced apertures in said plate in alignment with the apertures in said baffle, said plate being rotatable with respect to said baffle to vary the area of the openings provided by said apertures, means to fix said plate inadjusted position, a yieldable lining on the inner surface of said drum adjacent said plate, a riffle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said mat overlapping the upper edge of. said lining,

spaced inwardly extending annular ribs on said mat providing rifiles, a longitudinal inwardly extending fin on said mat, an elongated longitudinal recess in one side of said fin, said recess being closed at opposite ends, a second rifiie mat comprising a strip of yieldable material removablydisposed in said drum in engagement with the inner surface, the lower edge of said second mat overlapping the upper edge of said first mat, spaced rifiies on saidsecond mat of less depth than said first mentioned riffles, a longitudinal inwardly extending fin on said second mat and having an elongated longitudinal recess in one side closed at opposite ends, a third riffle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said third mat overlapping the upper edge of said second mat, spaced riflies on said third mat of less depth than said second mentioned riflies, a longitudinal inwardly extending fin on said third mat and having an elongated longitudinal recess in one side closed at opposite ends, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, a yieldable lining on the inner surface of said drum between said flange and said third mat and overlapping the upper edge of said third mat, means for feeding water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said riflles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

5. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baffle, a plurality of angularly spaced apertures in said baffle, an annular valve plate engaging the inner radial surface of said baffle, a plurality of angularly spaced apertures in said plate in alignment with the apertures in said baflie, said plate being rotatable with respect to said baflle to vary the area of the openings provided by said apertures, means to fix said plate in adjusted position, a yieldable lining on the inner surface of said drum adjacent said plate, a riflle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said mat overlapping the upper edge of said lining, spaced inwardly extending annular ribs on said mat providing riflies, a longitudinal inwardly extending fin on said mat, an elongated longitudinal recess in one side of said fin, a second rifile mat comprising a strip of yieldable material removably disposed in said drum and in engagement with the inner surface, the lower edge of said second mat overlapping the upper edge of said first mat, spaced riflies on said second mat of less depth than said first mentioned ritfles, a longitudinal inwardly extending fin on said second mat and having an elongated longitudinal recess in one side, a third rifile mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said third mat overlapping the upper edge of said second mat, spaced riffles on said third mat of less depth than said second mentioned riflies, a longitudinal inwardly extending fin on said third mat and having an elongated longitudinal recess in one side, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, a yieldable lining on the inner surface of said drum between said flange and said third mat and overlapping the upper edge of said third mat,

- means for feeding water and granular material through said"in1etopening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said riffles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

6. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baffle, a plurality of angularly spaced apertures in said bafiie, an annular valve plate engaging the inner radial surface of said baflie, a plurality of angularly spaced apertures in said plate in alignment with the apertures in said baffle, said plate being rotatable with respect to said battle to vary the area of the openings provided by said apertures, means to fix said plate in adjusted position, a riflle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced inwardly extending annular ribs on said mat providing riffles, a longitudinal inwardly extending fin on said mat, an elongated longitudinal recess in one side of said fin, a second riflie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said second mat overlapping the upper edge of said first mat, spaced riflies on said second mat of less depth than said first mentioned riffles, a longitudinal inwardly extending fin on said second mat and having an elongated longitudinal recess in one side, a third riflle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said third mat overlapping the upper edge of said second mat, spaced riflles on said third mat of less depth than said second mentioned riflles, a longitudinal inwardly extending fin on said third mat and having an elongated longitudinal recess in one side, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum, water and granular material retained by said riflies will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

' 7. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baflie secured to the inner surface of said drum at the lower end, a central discharge opening in said baffle, a plurality of angularly spaced apertures in said bafiie, means to vary the area of the openings provided by said apertures, a ritfle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced inwardly extending annular ribs on said mat providing rifiles, a longitudinal inwardly extending fin on said mat, an elongated longitudinal recess in one side of said fin, a second riflie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said second mat overlapping the upper edge of said first mat, spaced riffles on said second mat of less depth than said first mentioned rifiles, a longitudinal inwardly extending fin on said second mat and having an elongated longitudinal recess in one side, a third riflie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of saidthird mat overlapping the upper edge of said second mat, spaced riifles on said third mat of less depth than said second mentioned ritfles, alongitudinal inwardly extending fin on said third mat and having an elongated longitudinal recess in one side, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said riffles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

8. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baflie, a plurality of angularly spaced apertures in said baffle, means to vary the area of the openings provided by said apertures, a riffle mat comprising a strip ofyieldable material removably disposed in said drum in engagement with the inner surface, spaced inwardly, extending annular ribs on said mat providing riflies, a longitudinal inwardly extending fin on said that, a second riffle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said second mat overlapping the upper edge of said first mat, spaced riffles on said second mat of less depth than said first mentioned riflies, a longitudinal inwardly extending fin on said second mat, a third rifiie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, the lower edge of said third mat overlapping the upper edge of said second mat, spaced riflles on said third mat of less depth than said second mentioned riffles, a longitudinal inwardly extending fin on said third mat, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said rifiles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

9. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said bafl le, a plurality of angularly spaced apertures in said baffle, means to vary the area of the openings provided by said apertures, a riflle mat comprising a strip of yieldable material removably disposed in said drum and in engagement with the inner surface, spaced inwardly extending annular ribs on said mat providing riffles, a longitudinal inwardly extending fin on said mat, a second rifile mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced riffles on said second mat of less depth than said first mentioned rifiles, a longitudinal inwardly extending fin on said second mat, a third rifiie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced rifiies on said third mat of less depth than said second mentioned riffles, a longitudinal inwardly extending fin on said third mat, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum between said flange and the upper edge of said third mat. and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby 'upon rotation of said drum water and granular material retained by said riffles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

10. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baffle, a plurality of angularly spaced apertures in said baffle, means 'to vary the area of the openings provided by said apertures, a riflie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced inwardly extending annular ribs on said mat providing riffles, a longitudinal inwardly extending fin on said mat, a second riffle mat comprising a strip of yieldable material removably disposed in said drum and in engagement with the inner surface, spaced rifiles on said second mat of less depth than said first mentioned riflies, a longitudinal inwardly extending fin on said second mat, a third riflle mat comprising astrip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced riffles on said third mat of less depth than said second mentioned rifiies, a longitudinal inwardly extending fin on said third mat, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum'water and granular material retained by said riflies will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

11. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baflie, a plurality of angularly spaced apertures in said baffle, a rifiie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced inwardly extending annular ribs on said mat providing rifiies, a longitudinal inwardly extending fin on said mat, a second riflie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced rifiies on said second mat of less depth than said first mentioned riffles, a longitudinal inwardly extending fin on said second mat, a third riffie mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced rifiles on said third mat of less depththan said second mentioned rifflcs, a longitudinal inwardly extending fin on said third mat, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum and a plurality of inclined upwardly opening troughs extending into said drum through said dis charge opening whereby upon rotation of said drum water and granular material retained by said riifles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

12. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an

11 annular baflie secured to the inner surface of said drum at the lower end, a central discharge opening in said baflle, a riflle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced inwardly extending annular ribs on said mat providing riflies, a longitudinal inwardly extending fin on said mat, a second riflle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced -riflles on said second mat of less depth than said first mentioned riflles, a longitudinally inwardly extending fin on said second mat, a third riffle mat comprising a strip of yieldable material removably disposed in said drum in engagement with the inner surface, spaced riflles on said third mat of less depth than said second mentioned riflles, a longitudinal inwardly extending fin on said third mat, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said riffles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

13. A multiple gravity and float concentrator comprising a frame, a drum mounted for rotation on said frame on an inclined longitudinal axis, said drum being open at both ends, means for rotating said drum, an annular baffle secured to the inner surface of said drum at the lower end, a central discharge opening in said baflle, a plurality of riflle mats, each comprising a strip of flexible material removably disposed in said drum in engagement with the inner surface, spaced inwardly extending annular ribs on each mat providing riflles, a longitudinal inwardly extending fin on each mat, the riflles on each mat being of the same depth with such depth progressively decreasing from the lower to the upper mat, an inwardly extending annular flange at the upper end of said drum providing a central inlet opening, means for feeding water and granular material through said inlet opening into said drum and a plurality of inclined upwardly opening troughs extending into said drum through said discharge opening whereby upon rotation of said drum water and granular material retained by said riflles will be carried upwardly by said fins and deposited in said troughs, there being a separate trough for receiving material from each fin.

References Cited in the file of this patent UNITED STATES PATENTS 

